Recently, some mobile terminals, such as cell phones, are provided with a biometric authentication function. The mobile terminal provided with the biometric authentication function captures a biometric part by a camera provided on the mobile terminal, for example. However, depending on the size, specifications such as performance, or the like of the camera, there are cases in which the camera can capture only a portion of the biometric part that is used for the biometric authentication. For example, in the case of a compact mobile terminal provided with the biometric authentication function, such as a smartphone, the size of the camera that captures the biometric part is restricted, and an area of the biometric part that can be captured by one shot is small. It is difficult to capture the entire biometric part that is used for the biometric authentication by one shot.
When the biometric authentication is performed using the captured image of only a portion of the biometric part that is used for the biometric authentication, it is difficult to obtain a high authentication accuracy. One example of the biometric authentication includes a palm authentication that uses a vein pattern of the palm of a hand as the biometric part. When the palm authentication is performed using the captured image of only a portion of the palm, the authentication accuracy deteriorates compared to a case in which the captured image of the entire palm is used for the palm authentication.
Another example of the biometric authentication includes a fingerprint authentication that uses a fingerprint of a finger as the biometric part. For example, International Publication WO2004/097741 and Japanese Laid-Open Patent Publication No. 2002-024831 propose capturing the biometric part used for the fingerprint authentication a plurality of times, and performing the fingerprint authentication based on a large number of captured images. However, in this case, it is difficult to specify a suitable area of a registration template that is used for the fingerprint authentication to be matched to the large number of captured images of the fingerprint. In addition, in the case in which the biometric part such as the fingerprint is captured a plurality of times, the part of the biometric part that is captured each time may deviate according to habits, preference, or the like of the user of the mobile terminal. As a result, it is difficult to efficiently capture the biometric part that is suited for the biometric authentication. For this reason, even in the case in which the biometric part is captured a plurality of times, it is difficult to obtain a high authentication accuracy.
On the other hand, in the case in which the biometric part is captured by the camera of the mobile terminal, a capture area depends on the manner in which the user operates the mobile terminal. Hence, the area of the biometric part that is captured differs every time the biometric part is captured by the camera of the mobile terminal. In other words, different areas of the biometric part are captured when the biometric part is captured in a state in which the user holds the mobile terminal by the user's hand, and when the user moves the user's biometric part, such as the fingerprint, closer to the camera in a state in which the mobile terminal is placed on a desk, for example.
For this reason, in a case in which the capture area does not sufficiently capture the biometric part suited for the biometric authentication, for example, and the biometric authentication fails, the biometric part needs to be captured again, as proposed in Japanese Laid-Open Patent Publications No. 2003-085540 and No. 2007-122164, for example. When the biometric authentication fails and the biometric part needs to be captured again, the mobile terminal may urge the user to perform the capture operation again. However, it is difficult for the user to judge the capture area of the biometric part to be captured when performing the capture operation again. As a result, the number of times the biometric part needs to be captured again when the biometric authentication fails depends on the capture operation performed by the user, and the number of times may vary considerably. The convenience of the mobile terminal to the user deteriorates as the number of times the biometric part needs to be captured again increases. In addition, as the number of times the biometric part needs to be captured again increases, the probability of obtaining a successful biometric authentication may improve, however, there is no guarantee that the authentication accuracy will improve.
Hence, according to the mobile terminal provided with the conventional biometric authentication function, it is difficult to improve the accuracy of the biometric authentication.
Related art may include Japanese Laid-Open Patent Publications No. 2005-312749 and No. 2006-331239, for example.